Pieter Aertsen (1508 - 3 June 1575), called Lange Pier ("Tall Pete") because of his height, was a Dutch historical painter. He was born and died in Amsterdam, and painted there and in Antwerp, though his genre scenes were influential in Italy.

Pieter Aertsen was a Netherlandish painter active in his native Amsterdam and in Antwerp. A pioneer of still life and genre painting, he is best known for scenes that at first glance look like pure examples of these types, but which in fact have a religious scene incorporated in them (Butcher's Stall with the Flight into Egypt, University of Uppsala, 1551). Aertsen was the head of a long dynasty of painters, of whom the most talented was his nephew and pupil Joachim Beuckelaer.

As a youth, he apprenticed with Allaert Claesz. He distinguished himself by painting domestic scenes in which he reproduced articles of furniture, cooking utensils, and so on, with marvellous fidelity. Later in life, he began documenting historical scenes. Several of his best works, including altarpieces in various churches, were destroyed during the days surrounding the event known as the Alteratie, or "Changeover", when Amsterdam formally reverted to Protestantism from Catholicism on 26 May 1578 at the start of the Eighty Year's War. During the iconoclasm several paintings that had been commissioned by Catholic churches were destroyed.

An excellent specimen of his style is a painting of the Crucifixion, Aertsen was a member of Antwerp's equivalent of the Academy of St Luke. In the official books of the Academy he is known as "Langhe Peter, schilder" (Tall Peter, painter). His sons Pieter, Aert, and Dirck became acclaimed painters, and other notable pupils trained in his workshop included Stradanus and Aertsen's nephew, Joachim Beuckelaer.